''Bayardella'' is a genus of small,

neritiform ''Nerita'' is a genus of medium-sized to small sea snails with a gill and an operculum, marine gastropod molluscs in the subfamily Neritinae of the family Neritidae, the nerites.MolluscaBase eds. (2021). MolluscaBase. Nerita Linnaeus, 1758 ...

cylindrical shelled gastropods belonging to the family Planorbidae. They are native and endemic to Australia. Species of ''Bayardella,'' like other Planorbids, are non-operculate.

Description

The aperture (shell mouth) is typically almost as long as the entire shell with some specimens being described as 'almost abalone-shaped'. The species of ''Bayardella'', when adult, often display medium-sized shells that are usually 5-9mm in size. The shells often display heavy spiral ridges on the

periostracum The periostracum ( ) is a thin, organic coating (or "skin") that is the outermost layer of the shell of many shelled animals, including molluscs and brachiopods. Among molluscs, it is primarily seen in snails and clams, i.e. in gastropods and ...

, have a deep umbilicus and have a margin to the

columellar Lucius Junius Moderatus Columella (; Arabic: , 4 – ) was a prominent writer on agriculture in the Roman Empire. His ' in twelve volumes has been completely preserved and forms an important source on Roman agriculture, together with the ...

that is reflected and curved slightly but without a fold. The shells of ''Bayardella'', like other Planorbids, are typically sinistral.

Ecology

''Bayardella'' can be found living on the underside of stones and pieces of wood (i.e. fallen logs or branches) in the upper reaches of small streams and waterholes. ''

Bayardella ''Bayardella'' is a genus of small, neritiform cylindrical shelled gastropods belonging to the family Planorbidae. They are native and endemic to Australia. Species of ''Bayardella,'' like other Planorbidae, Planorbids, are non-operculate. Desc ...

'' cf. ''johni'' has also been observed living in the lower freshwater reaches of the Ross River, Townsville, Queensland. Due to the ephemeral nature of many of ''Bayardella'''s habitats, ''Bayardella'' are able to

aestivate Aestivation ( la, aestas (summer); also spelled estivation in American English) is a state of animal dormancy, similar to hibernation, although taking place in the summer rather than the winter. Aestivation is characterized by inactivity and a ...

on the underside of hard surfaces such as rocks and large pieces of wood.

Distribution

''Bayardella'' are endemic to the

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

n mainland. ''Bayardella'' are found in Western Australia, South Australia, the Northern Territory, Queensland, Victoria and New South Wales. However, ''Bayardella'' are only found in large populations on rare occasion in the Northern Territory. Elsewhere, they are found in small, often ephemeral populations.

List of species

Currently, there are two described species belonging to the genus ''Bayardella''. * ''

Bayardella cosmeta ''Bayardella'' is a genus of small, neritiform cylindrical shelled gastropods belonging to the family Planorbidae. They are native and endemic to Australia. Species of ''Bayardella,'' like other Planorbids, are non-operculate. Description T ...

'' (Iredale, 1943) * ''

Bayardella johni ''Bayardella'' is a genus of small, neritiform cylindrical shelled gastropods belonging to the family Planorbidae. They are native and endemic to Australia. Species of ''Bayardella,'' like other Planorbidae, Planorbids, are non-operculate. Desc ...

'' Burch, 1977 Type species: ''Plesiophysa (Bayardella) johni'' Burch, 1977 = ''

'' Burch, 1977 Original reference: Burch, J.B. (1977). A new freshwater snail (Basommatophora : Planorbidae) from Australia, ''Plesiophysa (Bayardella) johni''. ''Malacological Review'' 10: 79-80. Type locality:

Isdell River Isdell River is a river in the Kimberley region of Western Australia, named in 1898 by explorer Frank Hann after James Isdell, who was prominent in the region and later served as a member of parliament. The river rises in the Packhorse Range ...

, Walcott Inlet, north Western Australia. NOTE:

The Australian Museum The Australian Museum is a heritage-listed museum at 1 William Street, Sydney central business district, New South Wales, Australia. It is the oldest museum in Australia,Design 5, 2016, p.1 and the fifth oldest natural history museum in th ...

also recognises at least one undescribed of ''Bayardella''.

References

{{Taxonbar, from=Q20054203 Planorbidae Gastropod genera Gastropods of Australia